GET_PHYS_PAGES(3) Linux Programmer's Manual GET_PHYS_PAGES(3)

get_phys_pages, get_avphys_pages - get total and available physical page counts

#include <sys/sysinfo.h>
long int get_phys_pages(void);
long int get_avphys_pages(void);

The function get_phys_pages() returns the total number of physical pages of memory available on the system.
The function get_avphys_pages() returns the number of currently available physical pages of memory on the system.

On success, these functions return a nonnegative value as given in DESCRIPTION. On failure, they return -1 and set errno to indicate the cause of the error.

The system could not provide the required information (possibly because the /proc filesystem was not mounted).

These functions are GNU extensions.

These functions obtain the required information by scanning the MemTotal and MemFree fields of /proc/meminfo.
The following sysconf(3) calls provide a portable means of obtaining the same information as the functions described on this page.

total_pages = sysconf(_SC_PHYS_PAGES);    /* total pages */
avl_pages = sysconf(_SC_AVPHYS_PAGES);    /* available pages */

The following example shows how get_phys_pages() and get_avphys_pages() can be used.
#include <stdio.h>
#include <stdlib.h>
#include <sys/sysinfo.h>
int main(int argc, char *argv[]) { printf("This system has %ld pages of physical memory and " "%ld pages of physical memory available.\n", get_phys_pages(), get_avphys_pages()); exit(EXIT_SUCCESS); }

2019-03-06 GNU